In a small ball dissolve the yeast in warm water with a little bit of sugar and let stand until foamy.

In a kneading bowl, mix the milk, sugar, salt, egg and butter, add the yeast mixture and with a flour knead the dough. The dough is sticky so I recommend using a wooden spoon or a mixer. Cover the dough and let stand until doubled in size.

Meanwhile, make the filling. Whisk the egg yolk with sugar, then add the flour, cornstarch, vanilla and a little bit of milk. Bring the rest of the milk to boil, slowly add the egg yolk mixture and over the low heat cook until it thickens. Cover the surface with a cling foil and cool. Whip the heavy cream and mix with the custard filling.

Turn the dough on a floured surface and roll to 1cm thickness. Cut the doughnuts and place on a kitchen towel dusted with flour. Let stand until doubled in size.

Heat a frying oil over a high heat and fry the doughnuts until golden brown on both sides. Fry first the upper side of doughnuts. Drain them on a kitchen paper and let cool.

Spoon the filling into a piping bag fitted with a wide nozzle. Pipe the filling into a doughnuts.

For the topping, place a heaped teaspoon of powdered sugar, gently press for sugar to attach and use a blowtorch to melt the sugar until it caramelized. Serve immediately.**

*Or use your favorite doughnuts recipe.

** Since the caramelized sugar softens in time, I recommend you to caramelize only the doughnuts you will serve immediately.